High luminance and long life have been desired as recent LED lighting, and for sealing resin materials for sealing LEDs, high heat-resistance silicone sealing resins have been started to be used in place of conventional epoxy sealing resins. However, even in the case of using a silicone sealing resin, the application of a large current to an LED element particularly for increasing the luminance leads to increases in the temperatures of the LED chip and silicone sealing resin itself. For this reason, there has been a problem that a tackifier contained in the silicone sealing resin and organic components left during the silicone resin synthesis are colored to decrease the luminance.
In contrast, it is known that a metal oxide such as cerium oxide, titanium oxide, or iron oxide is added and blended as a thermal stabilizer in order to improve the heat resistance and ultraviolet light resistance of the silicone resin (see for example, Patent Document 1 and Patent Document 2). However, the effect of coloring prevention has not been confirmed on any organic matters in the silicone resin, other than silicone. In addition, the addition of the metal oxide to the resin material for LED sealing has the problem of decreasing the transparency, thereby leading to a decrease in visible light transmission, and thus resulting in a decrease in luminescent efficiency as an LED device.